Possible role of human interleukin-6 and soluble interleukin-6 receptor in hepatitis B virus infection

Human interleukin-6 has been shown to promote hepatitis B virus (HBV) infection. However, it is not clear whether this influence is the result of a direct interaction between interleukin-6 (IL-6) and the HBV envelope proteins or of a rather indirect mechanism. A direct interaction of IL-6 and the preS region of the large envelope protein (L-protein) of HBV has been reported. In this study we assessed the binding of IL-6 and of the IL-6 receptor subunits to the preS region of the L-protein of HBV. Binding of IL-6 and IL-6 receptor subunits sIL-6R and gp130 to preS was assessed by immunoprecipitation with recombinant preS proteins. In patient sera IL-6 and sIL-6R concentrations were analysed with respect to the course of hepatitis B infection during and after interferon-alpha (IFN-alpha) therapy. The IL-6 and IL-6 receptor subunits could not be precipitated with recombinant preS proteins. In sera of patients who responded to IFN-alpha therapy by virus elimination, a significant increase in sIL-6R concentration was measured. No increase in sIL-6R levels was seen in patients who did not respond to IFN-alpha. Hence, IL-6 and IL-6 receptor subunits do not bind to preS directly. A possible role for sIL-6R in the elimination of HBV infection is discussed.